A hydrolysis method to arrive at a different aluminosilicate zeolite has previously been disclosed in the inventor's U.S. Pat. No. 3,933,974. This hydrolysis method takes advantage of the hydrolysis of a hydrolyzable salt, such as Na.sub.3 PO.sub.4, to achieve the presence of the hydroxyl ion, which in turn allows for requisite pH of between 10 and 12 necessary for tetrahedral coordination of aluminum or silicon atoms with oxygen. This hydrolysis technique was developed at least in part to obviate the need for a template directive to acquire an aluminosilicate. The basic crystallizing reactants employed in the preparation of the aluminosilicate in the inventor's former mentioned patent are essentially xerogels. These are prepared by heating such materials as Ludox.RTM. or sodium aluminate and silica for 1 to 2 hours, filtering, washing with deionized water and heating for an additional hour in one molar NH.sub.4 Cl to obtain the xerogel (See Column 6, Example VI). As many as 41 experiments were previously conducted, some of which had a molar ratio of silica to alumina of greater than 20:1 and a molar content of Na.sub.3 PO.sub.4 to alumina of greater than 2.0. Experiments 16, 28, 29, 33, 36, 37 and 40 indicate that when these stoichiometric relationships are maintained, the resultant aluminosilicate (if not amorphous) is either a mixture of ferrierite, ferrierite and mordenite, or ferrierite, mordenite and adularia.
In an attempt to fine tune this method of preparation, i.e. to eliminate the cumbersome xerogel step of preparation, substitution was made in the crystallization of components comprising a colloidal silica (sometimes referred to as Ludox.RTM.) and an alumina hydrogel (sometimes referred to as Nyacol.RTM.). It was totally surprising to discover that this change of the silica and alumina reagent sources, i.e. from the former silica-alumina xerogel to colloidal forms of silica and alumina, resulted in the preparation of a ZSM-5 aluminosilicate, not a ferrierite. A second hydrolysis method is disclosed in Kouwenhoven et al, U.S. Pat. No. 3,758,667 for the synthesis of mordenite.
European patent application No. 98,641 indicates that a ZSM-5 composition of matter is prepared utilizing a fairly narrow stoichiometric range of silica to alumina of 20:1 to 50:1. However, even the formulation for this type of aluminosilicate must have a certain quantity of OH.sup.- ions provided by the presence of sodium hydroxide. While the European patentees recognized that a ZSM-5 aluminosilicate is prepared, without resort to an amine template director, it is still absolutely critical to their method of preparation that a substantially large quantity of sodium hydroxide be added, i.e. to provide the OH.sup.- moiety. Table 2 at page 5 establishes the molar ratios of the reagents wherein an exceedingly large quantity of sodium is present in the gel material. Also, Examples 1-14, when modified into Examples 15-18, arrive at a ZSM-5 material but without the use of a colloidal reactant and again with the presence of a relatively large quantity of sodium hydroxide as an additive to the gel.
It has now been surprisingly discovered that techniques of aluminosilicate manufacture can be greatly simplified and yet a manufacturer can still arrive at a ZSM-5 aluminosilicate as long as the proper stoichiometric relationship of the silica and alumina is maintained where the source of these materials is derived from a colloidal source.